Distinct ultrafast dynamics of bilayer and trilayer nickelate superconductors regarding the density-wave-like transitions

Abstract

In addition to the pressurized high-temperature superconductivity, bilayer and trilayer nickelate superconductors Lan+1NinO3n+1 (n = 2 and 3) exhibit many intriguing properties at ambient pressure, such as orbital-dependent electronic correlation, non-Fermi liquid behavior, and density-wave transitions. Here, using ultrafast reflectivity measurement, we observe a drastic difference between the ultrafast dynamics of the bilayer and trilayer nickelates at ambient pressure. We observe a coherent phonon mode in La4Ni3O10 involving the collective vibration of La, Ni, and O atoms, which is absent in La3Ni2O7. Temperature-dependent relaxation time diverges near the density-wave transition temperature of La4Ni3O10, while it is inversely proportional to the temperature in La3Ni2O7 above ∼150 K, suggesting a dramatic difference in the density-wave states of the two compounds and a non-Fermi liquid behavior of La3Ni2O7. Moreover, we estimate the electron-phonon coupling constants to be 0.05–0.07 and 0.12–0.16 for La3Ni2O7 and La4Ni3O10, respectively, suggesting a relatively minor role of electron-phonon coupling in the electronic properties of Lan+1NinO3n+1. Our work not only sheds light on the relevant microscopic interaction but also establishes a foundation for further studying the interplay between superconductivity and density-wave transitions in nickelate superconductors.